Semiconductor substrate processing apparatuses are used to process semiconductor substrates by techniques including, physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), pulsed deposition layer (PDL), molecular layer deposition (MLD), plasma enhanced pulsed deposition layer (PEPDL) processing, etching, and resist removal. One type of semiconductor substrate processing apparatus used to process semiconductor substrates includes a reaction chamber containing a showerhead module and a substrate pedestal module which supports the semiconductor substrate in the reaction chamber. The showerhead module delivers process gas into the reactor chamber so that the semiconductor substrate may be processed. In such chambers installation and removal of the showerhead module can be time consuming, and further, non-uniform film deposition (i.e. azimuthal variation) during substrate processing can occur if a lower surface of the showerhead module is not parallel to an upper surface of the substrate pedestal module.